The present invention relates to a liquid filter, comprising a holder element with an inlet and an outlet for liquid, a first container attachable to the holder element, and a filter body housed in said first container, said body being so dimensioned relative to said container, that an intermediate space is formed between the inside of said first container and the outside of said filter body, and is so arranged relative to said holder element that the inlet opens into said intermediate space, while a space inside the filter body opens into the outlet.
Two main categories of oil or fuel filters of this type are commercially available. Both consist of an outer cylindrical container of rigid material, usually sheet metal, and a filter insert of a fibrous material, e.g. cardboard folded in the form of a cylinder about a perforated tube. In the first case, the perforated tube is a metal pipe solidly joined to the container and having a threaded portion projecting up out of the container and being screwed securely to a threaded outlet connection on the holder element. The container with the filter insert forms a filter unit, which is commonly known as a spin-on filter. Such filters are relatively expensive since the container as well must be replaced when the filter is replaced. For processing discarded filters, the combustible material must be separated from the metal portions. In the second case, the perforated tube is a plastic tube, solidly joined to the folded cardboard cylinder and being held together therewith loosely in the container. When the filter is replaced, only the filter insert is replaced in the container, which after insertion of the new filter insert is screwed back onto the holder element. Filter replacement will therefore be less expensive than when the container itself must be replaced. Since the entire insert consists of combustible material, waste handling will be less expensive. The disadvantage is, however, that dirty oil or fuel deposits and other contaminants remaining in the container require the container to be cleaned before putting in the new insert. The cleaning requires the use of solvents to be effective. Neglected cleaning will increase the risk of contaminants entering the oil or fuel system of the engine and disrupting operation or causing damage to the engine.
The purpose of the present invention is to achieve a liquid filter of the type described by way of introduction which reduces the costs of replacing the filter in comparison with the first mentioned category above, while eliminating at the same time the risk of residual contaminants entering the oil or fuel system of the engine.
This is achieved according to the invention by virtue of the fact that said filter body is securely joined to a second container arranged in the first container and having, between its interior side and the outside of the filter element, an intermediate space into which the holder element inlet opens.
The second container forms a sort of liner inside the first container, and the contaminants are collected in the liner and are removed together with the filter upon replacement. There is thus no need to clean the outer container, which is reused after mounting of the new filter insert. If the outer container is made of a rigid material, e.g. sheet metal, the inner container can be made of softer material. It can, with advantage, be made of relatively soft plastic, since the liquid pressure against the walls of the inner container will be taken up by the outer container. This means that only combustible materials will be discarded when the filter is replaced.